Differential amplifiers are commonly used in various applications. A characteristic of such amplifiers is the ability of the amplifier to reject the input common mode signal, termed common mode rejection ratio, CMRR. A large CMRR is important in precision applications, such as in instrumentation. CMRR of an ideal amplifier is said to be infinite throughout its entire range of operation. However, practical amplifiers have CMRR specifications that are finite, with value that depends upon quality of internal circuitry and component tolerances which together tend to generate an offset. Amplifier offset varies with common mode input voltage. It would be advantageous to trim CMRR so as to improve amplifier performance.